In the airplane industry, it is well known that the maintenance of a level of comfort in the cabin for the passengers and crew is important and necessary. The maintenance of desired ambient conditions includes interior cabin pressure, relative humidity and temperature. This comfort level is true in all types of airplanes including private airplanes and military airplanes. In airplane cabins of large commercial airplanes, comfort level is particularly important since modern commercial airplanes have passenger loads in the hundreds.
In the case of a large commercial airplane, the airplane flies at tens of thousands of feet above sea level and well above the clouds. During daytime, these commercial airplanes, with multiple windows, encounter hours of solar radiation. Because of the many windows, it is extremely important to protect the interior from the potentially excessive levels of infrared heat radiation in the cabin resulting from the solar radiation. In this regard, it is also important to avoid excessive heating of the internal cabin because this places a burden on the air conditioning system which thereby places a burden on fuel efficiency in order to maintain the cabin temperature at a suitable comfort level. In addition, the excessive heating could raise the temperature of parts of the window assembly well above their allowable limits.
One of the principal ways to reduce the amount of heat radiation caused by the transmission of infrared heat from solar radiation is to provide a suitable design for the windows. Specifically, it is important to reduce the amount of infrared heat radiation from entering the cabin through the many passenger windows provided in a commercial jet airplane.
Present airplane window designs involve a “stack” of transparent components including, for example, an outer pane, an inner pane, for some airplane models, an interlayer or a bonding layer between the two panes, and an innermost dust cover for the cabin interior. In some cases, in modern aircraft, there is a substantially transparent panel of an electronic dimmer window (EDW). EDW is a device to control light transmission into the cabin via electronic apparatus. In addition, in some modern airplane windows, a solar reflective coating, containing particles of metallic pigments, has been applied on the inboard surface of the inner pane of the window assembly. Such coatings are available from both PPG Industries and GKN Industries. Such coatings are available with both silver and gold particles. Although such gold containing coatings have been effectively used, still further effective reduction in the amount of infrared heat from solar radiation passing through the windows into the cabin is considered to be highly desirable. It would be highly desirable to further reduce solar heat transmission so as to maintain the comfort level in the cabin for the passengers, but it would also, importantly, increase fuel efficiency and durability of the window system. Any such increase in fuel efficiency in an airplane is clearly highly beneficial. The window assembly to be described herein fulfills such a need.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such approaches with the present disclosure as set forth in the remainder of the present application including the drawings.